Difference Between Dupelx Steel S32205 & S31803 Alloy
Posted on November 18, 2021 at 10:20 AM
Duplex Stainless Steel is intended to give:-
- Greater corrosion resistance, notably against chloride stress corrosion and chloride pitting corrosion.
- More strength than typical austenitic stainless steels such as Type 304 or 316.
- When compared to austenitic stainless steel, the key changes information are that duplex steels have a greater chromium concentration, 20–28 percent; a higher molybdenum content, up to 5 percent; a lower nickel content, up to 9 percent; and 0.05–0.50 percent nitrogen.
- Both the low nickel content and the high strength (which allows for the use of thinner sections) provide substantial cost savings.
Applications of Duplex Stainless Steel are majorly in the two most crucial industries i.e, the offshore oil and gas sector for pipework systems, manifolds, risers, and other components as well as the petrochemical industry for pipelines and pressure vessels.
How is Duplex Stainless Steel better than other Stainless Steel?
- Duplex steels offer stronger strength in addition to better corrosion resistance when compared to 300 series stainless steels.
- Type 304 stainless steel, for example, has a 0.2 percent proof strength of about 280 N/mm2 whereas a 22 percent Cr duplex stainless steel has a baseline 0.2 percent proof strength of around 450 N/mm2, and a super duplex quality has a minimal of 550 N/mm2.
- Minimum yield stress values are almost two times higher as in austenitic stainless steel.
- Because duplex grades permit for smaller sections, they are appealing when mechanical qualities at room temperature are needed.
What are the various grades of Duplex Stainless Steel?
Duplex stainless steels are often classified into three categories based on their resistance to pitting corrosion, as measured by the pitting resistance equivalent number, PREN = percent Cr + 3.3 percent Mo + 16 percent N.
Standard Duplex (PREN range: 28–38)
Normally, EN 1.4462 is the grade (also called 2205). It is characteristic of mid-range houses and is maybe the most often used nowadays.
The super-duplex (PREN range: 38-45)
Usually, grades EN 1.4410 and up to so-called hyper duplex grades (PREN: >45) were created subsequently to fulfill special needs of the oil and gas sectors, as well as the chemical industries. They have better corrosion resistance and strength, but they are more difficult to process because greater levels of Cr, Ni, Mo, N, and even W stimulate the production of intermetallic phases, which reduces the steel's impact resistance significantly. Faulty processing will lead to poor performance, hence consumers should only work with recognized suppliers/processors. Deepwater offshore oil production is one of the applications.
Grades for lean duplexes (PREN range: 22–27)
Grade EN 1.4362, for example, has recently been designed for less demanding applications, notably in the building and construction sector. Their corrosion resistance is comparable to that of normal austenitic grade EN 1.4401 (with a little advantage in stress corrosion cracking resistance), and their mechanical qualities are superior. When strength is crucial, this may be a huge benefit. This grade can be utilized for bridges, pressure vessels, and tie bars.
UNS S32205
UNS S32205 is ferritic-austenitic duplex steel having a ferritic-austenitic microstructure. In the annealed state, the alloy contains around 40-50 percent ferrite.
The duplex microstructure combines the toughness of ferritic grades with the corrosion resistance of austenitic grades. It is not unusual to see the metal employed as a realistic answer to the Achilles’ heel of stainless steel, chloride-induced stress cracking.
When compared to 317L stainless steel, UNS S32205 offers better resistance to chloride pitting and crevice corrosion. The alloy has excellent corrosion resistance to saltwater and most sulfuric acid concentrations. UNS S32205 duplex stainless steel is also resistant to sulfide stress corrosion cracking (sour-gas environments). The large concentrations of chromium, nitrogen, and molybdenum contained in UNS S32205 are largely ascribed to its excellent composition and hence efficiency.
Properties of UNS S32205:-
| DENSITY | MELTING RANGE | POISSON’S RATIO | ELECTRICAL RESISTIVITY |
| 7.1 g/㎤ | 1385-1443℃ | 0.3 | 8 x 10^-7 Ωm |
Mechanical Properties:-
| Coefficient of Thermal Expansion µm/m℃ | Thermal Conductivity/ kcal/ (hr.m.℃) | Modulus of Elasticity/ x10 5 MPa |
| 14.4 | 11.9 | 1.93 |
Applications:-
- Systems that use seawater
- Pumps and valves for seawater
- Vessels for chemical processing, pipework, and heat exchangers
- Scrubbers for FGD
- Digesters for pulp mills and bleach washers
- Food processing machinery
- Pipeline in the oil field
UNS 31803
UNS S31803 is a duplex stainless steel grade with a 50:50 austenite, ferrite microstructure. The material incorporates strong mechanical strength and ductility with moderate to good corrosion resistance in a variety of settings.
This Duplex Steel UNS S31803 material is typically supplied in the annealed form. The yield strength of the material in an annealed state is roughly 450 Mpa.
The A276 S31803 Material alloy may be used effectively as a substitute to austenitic stainless steels of the 300 series. In fact, it may be utilized as a replacement in practically any application requiring great mechanical strength and low weight.
Properties of UNS S31803:-
| DENSITY | TENSILE STRENGTH | YIELD STRENGTH | ELONGATION | HARDNESS,BRINELL |
| 7.82 g/㎤ | 621 MPa | 448 MPa | 25.0% | 293 |
Applications:-
- Filters for flue gases
- Chemical storage tanks
- Exchangers of heat
- Components of acetic acid distillation
How are UNS 32205 and UNS 31803 different from each other?
The first standard for duplex stainless steel was preserved as UNS S31803. However, a few of the industry's major producers were routinely manufacturing this grade to the upper limit of the permissible standard. This mirrored their intention to maximize the alloy's corrosion performance, which was supported by the invention of the AOD steelmaking process, which allowed for finer composition control. Furthermore, it enabled the degree of nitrogen additions to be regulated rather than simply being present as a background element. As a result, the best performing duplex grade tried to maximize chromium (Cr), molybdenum (Mo), and nitrogen levels (N).
A new standard, UNS S32205, was created to identify the duplex stainless steel produced at the upper end of the composition range. Duplex stainless steel manufactured to the S32205 (F60) caption will completely meet the S31803 (F51) caption, but not the other way around. As a result, S32205 may also be dual-certified as S31803.
Workability S31803 and S32205
They have strong thermal strength in the region of 9501150°C, which is comparable to Type 430. However, below 900°C, it displays a significant rise in strength. In terms of cold workability, caution is required since proof stress is high and elongation is poor when compared to Type 304.
Weldability Standards S31803 and S32205
TIG welding, shielded metal arc welding, and plasma welding may all be conducted in the same way as with normal austenitic stainless steel. Welding electrodes are recommended. There is no need for preheating or post-heating. To avoid the production of intermetallic, the interpass temperature in welding should not exceed 100°C.
Heat Treatment S31803 and S32205
Solution annealing should be carried out at temperatures of 1040°C or above, followed by quenching in water or quick cooling by other methods.
Pickling S31803 and S32205
Pickling uses a combination of nitric acid and fluoric acid. However, since descaling is more difficult than with Type 304, alkali immersion before acid pickling and, if feasible, shot blasting is particularly effective.
S31803 vs. S32205: Which is better?
UNS S31803 and S32205 are alloyed with more similarities than differences. For starters, they are both stainless steel with comparable elemental compositions. UNS S31803 and S32205 are both members of the duplex 2205 family, which implies they are approximately equally composed of austenite and ferrite. Second, they are both very strong and long-lasting alloys. S31803 and S32205 are both used in some of the most difficult and inhospitable manufacturing processes that need materials that can withstand repeated and continuous rides through the wringer.
The most visible difference between the two is that UNS S32205 has a larger nitrogen concentration, which adds another layer of protection to an already firm surface. The presence of treated nitrogen provides an extra layer of protection against any corrosive substances attempting to attack and eat away at the steel solution. This improved corrosion resistance offers UNS S32205 a minor but considerable advantage over its nearest competitor.
The addition of nitrogen has increased its capacity to defend itself, which is the frosting on the cake. What was formerly a very trustworthy piece of duplex steel now has an enhanced inclination to defend against wear and tear and maintain the quality of any application.
Stainless steel at Amardeep Steel:-
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